Help Me Diagnose This (please) - Part 2

[CC57]

'99 Suburban with a 5.7 liter.

 

Ok, so here we are in “Help Me Diagnose This – Part 2”.

 

For those that missed part 1, what I thought may have been a bad thermostat or whatever turned out to be a low coolant level in the radiator.

 

Which now brings up the question, why is the level down? And why do I have to keep adding water?

 

So here are some symptoms:

 

The temp gauge rises steadily and in what I would consider a normal fashion up to about the midway mark between 100 and 210 (around 160, right?) and pretty much holds there. No erratic deviations up or down. But I keep having to add water to the rad.

 

Topped it off last night (ran up the revs, topped it off and put on the cap with the revs up), made a trip to the airport and back to pick up in for Christmas relatives (that’s a whole another horror story …). Temp steady midway between 100 & 210 during the 100 or so miles traveled.

 

This morning, had to add 2 cups to top off the rad. This is the 3rd time I’ve had to add water.

 

Checked the oil dipstick. Level ok and the oil did not appear to have that milky oil/water mix look to it.

 

No visible leaks around the rad, on the engine and on the ground below the car

 

Should I drain out more oil (2 or 3 quarts) and check again?

 

Or …? Suggestions.

 

And thanks for helping me y’all.

[97car]

Check your intake bolts, the 5.7 I helped rebuild had 2 that rusted and were broken, no visible leaks from above, it is in the aluminum side of the intake manifold. It had leaked so long the bearings were toast when they had me look at it, it ran normal temp, just low oil pressure when warmed up and a slight nock.

[Pappy_GT13]

Find someone with a pressure tester & have them pressurize the system & look for leaks. Check where heater hoses connect, radiator- hoses- tanks- core, check a/c drain for leaking heater core. Get underneath & look at core plugs- trace of coolant from back plugs usually shows at trans. dust cover. If there are NO visable leaks, check exhaust for coolant smell/excessive steam. If you smell coolant burning, Then check intake for coolant passage leaking coolant into closest intake tract. This will usually show up on the spark plugs, cyl's burning coolant will be 'cleaner' looking.

 

Hope this helps.

 

BTW, if the rise in temp as engine warms spikes & drops back to a significantly lower temp, replace the therostat. It is sticking & opening suddenly instead of gradually like it should. Thermostats wear out & are usually the least expensive part to replace.

[KISS_Racing]

Im with Pappy. Pressure test the sytem.

[HiTech]

Im with Pappy. Pressure test the sytem.

yep pappy took that right out from under my fingers ... but one little thing .....if you fill the radiator to the top completly. the cap will let out enough coolant for exspansion ... two cups isnt very much water ..my intreped looses that much when we fill it up to the top ..then levels out ....my jeep does the same thing ...dont add anymore and drive it alittle and see where it ends up ..you may find it to be ok ...also if it still looses coolant check your floor under your carpet and make sure its dry ..heater core could have a small leak ...that you wont find looking at the motor ..you also could look and see if coolant is comeing from your ac .drain ....in which you could mistake as ac water if you run the ac..... and lay down under the truck . take a light and check your water pump weep hole ..water pumps will leak .and not be enough to build a puddle .... found that problem to many times ...and it will not always show up under a pressure test ...sometimes it will depend on where the water pump shaft stops when you turned it off. ... ...found that to be true a few times ...anyway if you cant find something and it still keeps do it ..find a good shop to take it to . that would be cheaper than a burnt motor ...

[CC57]

First of all, a sincere thank you to all who have responded. Hopefully I can return the favor in some way in the future.

 

After filling it today (with the 2 cups worth, as measured by pouring the water from an 8 cup measuring container) I did some running around purchasing Christmas gifts. Just got home a few minutes ago, so I'll let her cool off over night, check it in the morning and see how it looks. And if it doesn't look too bad, maybe measure how far the water level is below the fill cap, not refill it and drive around some more and see how much or if the level changes. I'll also get the creeper out and check the bottom out thouroughly.

 

Also, I'm starting to think if it even if it is leaking, I don't think it's leaking in to the block via the heads or intake manifold or wherever. Why? Because I would think I would be able to detect some oil in the water in the radiator. But when I checked some of the water for the radiator, it was clean. Anyone agree?

 

So I'll watch the fluid level, and if it keeps going down, I'll attempt to locate a reputable mechanic (sorry, but I'm a bit cynical when it comes to most mechanics) and take it in for pressure testing/troubleshooting.

 

Crossing my fingers - I need my $s for fun stuff, like a new set of shocks for my Mod, maybe attend a driving shcool, more methanol, ....

[KISS_Racing]

CC57,

 

While refilling your radiator what is the level in your overflow? I had a mazda truck that this happened to me on. On a 160 mile trip (Kerrvile and back + a little around town driving it would use only what was in the overflow. Turned out to be a leak in the head gasket between a water passage and one of the cylinders. Did head gasket and trouble solved.

[flyingaces]

THIS IS A VERY COMMON PROBLEM FOR THE 96-99 5.7L VORTEC ENGINES. THEY HAVE WEAK INTAKE GASKET'S. SOME TIMES THEY ARE A HARD TO FIND LEAK UNLESS YOU PRESSURE TEST THE SYSTEM. THEY USUALLY LEAK ON THE BACK DRIVERS SIDE OFF THE ENGINE AND IT RUNS DOWN ON THE EXHAUST, AND DOWN THE OIL FILTER. BEFORE I OPENED MY OWN AUTOMOTIVE SHOP I MANAGED A FLEET OFF ABOUT 120 CHEVY TRUCKS, SOO I HAVE SEEN THIS A TIME OR TOO, ALSO IF YOUR SYSTEM HAS ONLY WATER IT WILL BE HARDER TO NOTICE, SINCE WATER EVAPORATES AND COOLANT DOES NOT. HOPE THIS HELPS.

[CC57]

Well in case any one was curious...

 

Had a pressure test run. Leak is on the intake manifold, passenger side, up near the front (above the #2) cylinder.

 

Got a guy at a large chevy dealer who said he would do the job, parts and all, for $250. I said "SOLD". Heck, gasket set alone is about $65 from the local parts house. And I really don't feel like having to remove all the EPA-mandated sensors and hoses and on and on....

 

On my Mod, it's different story. I would do it because the whole job might take 3 hours.

 

Anyway, I learned a bit from all of this. Thanks again for all of the replies.

 

One last question: heard it may not be a bad idea to change out the water pump at the same time. Didn't get a chance to go into detail as to why, but wonder if there may be something supporting that line of thought. Any one?

[97car]

I just hope the lower end survived thru this, the timing on your truck would have had to been set on the computer anyway, same area that occurred on the 98 model I rebuilt.